Chlorinated and/or fluorinated propenes are known to be useful as monomers in the manufacture of plastics and resins and also find use as chemical intermediates in the manufacture of, e.g., hydrofluoroolefins. Many such compounds are also known to be useful as nematocides and insecticides, and in fact, this may be their predominant use.
The commercial availability of these compounds may be undesirably limited by the processes typically utilized in their manufacture. For example, chlorinated and/or fluorinated propanes have been reacted with oxygen and in the presence of a catalyst and at high temperatures to produce chlorinated propenes. Desired chlorinated and/or fluorinated propenes have also been obtained by dehydrochlorinating trichloropropenes in the presence of oxygen or by reacting dichloropropenes with chlorine and/or allyl chloride and/or chloropropenes to provide the desired chlorinated propene. However, all of these processes are complicated multi-step processes, and many require the use of catalysts and thus, the removal of one or more catalysts from the product.
The process most commonly relied upon for the production of one exemplary chlorinated propene, 1,3-dichloropropene, is actually a process for the production of allyl chlorides. In such processes, the thermal chlorination of propene provides about 70-85% selectivity to allyl chloride and 15-30% dichlorinated byproducts. Up to about 50% of the byproducts, in turn, may typically comprise about 50% 1,3-dichloropropene, with the remainder consisting of other chlorinated propenes, 1,2-dichloropropane, six carbon olefins and other chlorinated six carbon compounds.
Although this process accounts for a large majority of the production of 1,3-dichloropropene, it is suboptimal at least because it links the production of 1,3-dichloropropene to the production rate and demand for allyl chloride. The conventional process can also be found lacking when the end product is desirably a single isomer rather than a racemic mixture. The cis isomer of 1,3-dichloropropene is known, for example, to be about twice as active as a nematocide as the trans isomer. However, while the cis isomer is slightly more volatile than the trans isomer, and therefore should be separable by fractional distillation, it has been found that both this distillation and any subsequent isomerization of the trans isomer are greatly impeded by the presence of a small proportion of six carbon olefins that boil very close to the boiling temperature of the dichlorinated propene fraction.
Although simplified, one-step processes have been developed for the manufacture of chlorinated and/or fluorinated propenes, these processes can have limited commercial applicability due to their limited throughput. Whether multi-step or one-step, many of the conventional manufacturing processes for the production of chlorinated and/or fluorinated propenes may typically result in the formation of large quantities of reaction by-products that must then be separated from the product and disposed of, typically at great expense, further limiting their commercial potential.
It would thus be desirable to provide improved processes for the production of chlorinated and/or fluorinated propenes. More particularly, such processes would provide an improvement over the current state of the art if they could by decoupled from the manufacture of products in which they are produced as by-products, or as a portion of a mixture of by-products from which their separation is difficult. Cost savings and/or improvements in reaction selectivity would also provide commercial advantage and be appreciated by the art.